1. Field of the Invention
The present invention relates to a variable nozzle control device and a variable geometry turbocharger with the variable nozzle control device.
2. Related Background Art
For example, the variable geometry turbocharger is commonly adopted in diesel engines. The variable geometry turbocharger has variable nozzles to adjust a flow rate of exhaust gas. An opening of the variable nozzles is controlled by an actuator (e.g., a stepping motor or a DC motor). For accurate control of the opening of the variable nozzles, an important factor is a reference value for the opening of the variable nozzles. In order to eliminate dispersion of the opening of the variable nozzles, there are proposed technologies of learning the reference value for the opening of the variable nozzles. One of such technologies is variable nozzle full close learning. In the variable nozzle full close learning, the reference value is determined to be an opening detection value in a full close state of the variable nozzles with the engine at a stop.
A conventional technique of execution of the variable nozzle full close learning is, for example, the technology described in Japanese Patent Application Laid-open No. 2002-4869. In the technology described in this application, an arm is connected through a unison ring to a plurality of movable vanes (variable nozzles), this arm is moved by a stepping motor, and a position regulating member is provided so as to engage with the arm. In this configuration, the arm is moved by the stepping motor to be brought into contact with the position regulating member and the opening of the movable vanes (in the full close state) at that time is defined as a reference position.